H2O2 spray solution

Does a diluted solution of hydrogen peroxide spray turn mushrooms toxic? I sprayed a diluted solution on a cake between flushes to get rid of fungus gnats. I ended up getting a good second flush although the caps were darker in this flush. Then I read on another forum that someone almost died from eating a mushroom treated in this way because peroxide is poisonous to humans. Seems bogus to me. I haven't tried the mushrooms from this second flush yet.

Hello!

When you use hydrogen peroxide H2O2 it breaks down into water + oxygen gas (so you may observe water and some bubbles on the mushroom cake).

2 H2O2 –> 2 H2O + O2

That's it!

Mycelium or mushrooms don't absorb and retain H2O2 as is. And it's not harmful for you unless you drink it, inhale or leave on the skin (especially damaged skin) for too long, or use it too often or in high concentrations.

Hydrogen peroxide works as an oxidizer. Hence, can damage mycelium cells and mushroom fruit body tissue, as well as mold spores, bacteria cells and any living cells.

Regular 3% peroxide, that you can buy at any pharmacy, is considered a low concentration. It's commonly used (not diluted) for people and for some types of mold treatments. It doesn't damage mycelium too much and doesn't affect mushrooms' look.

Concentrated peroxide 10%-35% is much more dangerous! But it is used for industrial purposes and it's not for human use or mushrooms. Such peroxide can literally burn mycelium and shrooms won't grow at all.

Regarding fungal gnats, spraying alone won’t work well enough. Why? Because their larvae and flying adults live in the substrate, sometimes deep inside the cake. So you need to soak your mushroom cake for about 20 minutes in diluted 3% peroxide (1 part of peroxide to 10 parts of water). Toss the cake if it doesn't help get rid of the flies, otherwise you can dramatically increase their population and it will be a problem for your future grows.

Btw, do you have any plant pots with soil near your box with mushroom cake?

One more point! Changes in color, size, and shape from one flush to the next are absolutely normal and it happen soooo often! As an example, you can compare mushrooms from flush 1 to flush 5 in the guide here - check out pages Flush #1, Flush #2 Flush #3, ...

And finally, based on my experience and experience of other growers on Shroomok forum and discord, we've used H2O2 many times and never had any issues. Peroxide works at the moment of use and breaks down quickly when exposed to organic material (substrate, mycelium). So it seems like the guy you mentioned had a completely different problem.

Hope I covered all your questions :-)

Thanks for the info! I'm new to this. First successful grow I've had. I figured the guy who said he almost died probably had some other issue as I have seen H2O2 spray as a common solution to contaminants on all the forums. I sprayed a diluted solution, about .6%, on my cake for several days and it did get rid of the gnats. Then I had a good second flush. I have since dunked, in regular distilled water, and am attempting fruiting conditions again. Nothing yet but the dunk was only a week or so ago so I am patiently waiting. We do have other potted plants in the house that were the source of the pesky gnats. We have started spraying the soil on those and it seems they are all gone now. I'm glad I found this forum. Seems like a great source of info. Had I found this sooner I might have succeeded in my first two attempts...

You've got what I meant when I asked about plant pots ;-) Yeah, they're one of the main vectors of flies contamination. Another vector could be poor bulk substrate pasteurizarion.

Anyway, your treatment works and that's great👍

What happened with your previous 2 attempts? Mold contam? Do you do everything yourself or do you use ready-made growkits? Just wondering :-)

I'm also glad you found this forum. Better late than never ;-) Always happy to help!

The first attempt was a monotub setup but I bought the grain and the substrate. It stalled out and eventually got contaminated. I think I didn't let the grain colonize enough before adding to substrate. I then bought two grow bags. One ended up smelling like wine and getting cobweb mold so I tossed it. The other one has led to two flushes and pins starting to form for a third. I also have another grow bag colonizing and it's coming along nicely so far. I've learned a lot through these attempts. It's fun to watch the whole process.

So you're already an experienced grower haha

Yeah, mushroom growing is an amazing process for sure!

Hope you'll get a proper 3rd flush🤞

Don't forget to make a short update here, okay? ;-)